# **9.126 The MOS differential amplifier shown in Fig. P9.126 utilizes three current mirrors for signal transmission: Q4−Q6 has a transmission factor of 2 [i.e., (W/L)6/(W/L)4 = 2], Q3−Q5 has a transmission factor of 1, and Q7−Q8 has a transmission factor of 2. All transistors are sized to operate at the same overdrive voltage,  VOV . All transistors have the same Early voltage  VA . Q3 Q4 Q1 Q2 VDD VDD Q6 Q7 Q5 Q8 vo I Figure P9.126 (a) Provide in tabular form the values of ID, gm, and ro of each of the eight transistors in terms of I, VOV, and VA. (b) Show that the differential voltage gain Ad is given by A d = 2gm1ro6 ro8 = VA/VOV (c) Show that the CM gain is given by  A cm   ro 6 ro8 R SS 1 gm7ro7 where R SS is the output resistance of the bias current source I. [Hint: Replace each of Q1 and Q2 together with their source resistance 2R SS with a controlled current-source v icm/2RSS and an output resistance. For each current mirror, the current transfer ratio is given by A i  Ai (ideal) 1− gm1ro  where gm and ro are the parameters of the input transistor of the mirror. (see Problem 9.125 above.)] (d) If the current source I is implemented using a simple mirror and the MOS transistor is operated at the same V OV, show that the CMRR is given by CMRR = 4VA/VOV2 (e) Find the input CM range and the output linear range in terms of V DD,  Vt  , and  VOV

This content is for Premium members only.
sign up for premium and access unlimited solutions for a month at just 5\$(not renewed automatically)